Problem: ${10 \div 0.4 = {?}}$
$ {10 \div 0.4 = 10 \div \dfrac{4}{10}} $ $ {\phantom{10 \div 0.4} = 10 \div \dfrac{2}{5}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {10 \div \dfrac{2}{5} = 10 \times \dfrac{5}{2}} $ $ {\phantom{10 \div \dfrac{2}{5}} = \dfrac{10 \times 5}{2}} $ $ {\phantom{10 \div \dfrac{2}{5}} = \dfrac{50}{2}} $ $ {\phantom{10 \div \dfrac{2}{5}} = 25} $